And time/average speed was the similiar with the Yamaha? Both are "umlimited", support up to 45km/h? The Yamaha has 500Wh?
If I compare my Stromer Class 3 45kph/28mph rear hub motor ebike with my 25km/h Creo, the results with full motor support on both (what I never do on the Creo) are like:
pure road&flat: Stromer average speed 23mph and about 30Wh/mile, Creo 20mph (16mph motor limit) and about 1Wh/mile
road and "forrest highways" and almost flat and some traffic lights (my usual way to work): Stromer average speed 21mph and about 29Wh/mile, Creo 18-19mph and about 2Wh/mile
pure road&hilly: Stromer average speed 20mph and about 28Wh/mile, Creo 14mph and about 6Wh/mile
gravel (offroad with a little bit off road and hilly, my usual use case for the Creo): Stromer maybe 16mph (and a lot of pain for the heavy rear wheel without suspension and my back) and 20Wh/mile, Creo 13mph and about 6Wh/mile
The main difference apart from the bad offroad usability of the Stromer is the fun the bikes give you with low ore no support. Stromer is great for high speed but terrible without support and even no fun with low support in Level1. This takes 10-15Wh/mile, depending if it's flat or hilly (but I've never used it for a whole battery, it's only acceptable for a few miles to reach your destination (or together with slower riders). Creo an the other side is great without support or only little support, everything between 0-4Wh/mile is great (I normally don't use/need more).
given that i don't use the motor on flats and brake a LOT on the corresponding downhills to these, a rear-drive hub with regenerative braking would likely result in a huge boost in range for my use case, presuming that it didn't introduce excessive parasitic drag when turned off. another very interesting concept would be a tiny battery, say 50wh, which would provide power for at least a 2000' climb for me, which charged by sapping 10% of my input power while pedaling on the flats. of course with the math above it would take 2.5 hours of riding at 200w to charge the thing, so the ride would have to start with flats, not hills, but it would be really interesting to have an e-bike which never used power from the wall, only from your legs. essentially it would "flatten" hills by slightly steepening the flats!
Regenerative braking offer only very few ebikes, I know only two brands today (Stromer and Klever). Both with similar and very heavy motors, the rear with tires wheels ways about 8,5-10kg/18-22lbs depending on the model! There is no small assist drive like SL or Fazua with a small light hub motor with regenerative braking. All the small ones like Mahle/ebikemotion X.35 and others are without that, as this needs quite some effort/costs, extra weight, and bigger motor and battery to produce and stand the currents.
And the effect is much less than one would expect, on my Stromer on usual rides (not that hilly...) I get maybe 2% back. On very hilly rides/mostly in real mountains it would be 5-10%. You can get more if you always put in Regenerative breaking on all downhill parts going down only with 15-20mph. But I guess most of us will let it roll there and enjoy speeds up to 40mph.
You also never get back all energy with regenerative braking, there are quite some losses, usually you can recover only maximum 50-60%.
I tried sometimes to recharge my battery siginficantly with "full power pedaling" on slight downhills with full regenerative breaking or with some in the flat. It's not fun and you are fed up with it after 2-3% recharging.